It is a strange sight on the WHO COVID-19 map: A large landmass in the IJsselmeer (the large fresh water inner-lake in the Netherlands) that does not exist in the real world. On the left side of the image below is the image from the WHO site, on the right the Netherlands how they are (correctly) shown on Google Maps.
Now, how does water change into land on a map? Well, in this case, it is more than a glitch in the mapping-software: there have been plans for this land mass for over more than 100 year. But they have been abandoned.
The inner lake, IJsselmeer, was a sea until the 1930's. This sea, called the Zuiderzee (Southern-Sea), had been contained by dikes, but was prone to cause severe floodings when storms pushed water from the North-Sea into the inlet of the Zuiderzee.
From around the 1850's, plans were made to drain this large and dangerous inner-sea, not only to protect the surrounding country, but also to develop valuable farming ground, as had earlier successfully been achieved with smaller lakes.
At the end of the 19th century, a committee chose the engineer Cornelis Lely to develop plans for this massive reclamation of the Zuiderzee. Based on detailed investigations of the seabed, but also on the need of maintaining a bassin for the river the IJssel, Lely planned 4 areas to be drained (in Dutch these are called polders), and a large enclosure dam at the inlet of the inner sea. But it was not until 1918, largely influenced by a devastating flood in 1916, that the government officially adopted the plans. By that time, Cornelis Lely had become minister of Water Management.
Although eventually several changes were made, most of the original 1892 plan by Lely was maintained. The forms of the polders seems a bit randomly chosen, but the contrary is true: it is of no use to reclaim sandy grounds that cannot be used for farming. The form of the polders strictly follow the borders between the areas where the seabed is composed of fertile clay, and the sandy seabed, caused by deposits from the river the IJssel.
Enclosure Dam and Wieringermeerpolder
The first project was the building of the enclosure dam, the Afsluitdijk. Aim was to drastically shorten the coast line. First, from 1920 to 1924, a 2.5 kilometer long dam was build from the mainland to the Isle of Wieringen. From the other end of the by then former-island, work on the main dam started in 1927.
At the same time, a dike was build from Wieringen to the south, connecting to the mainland near the village of Medemblik. This dike was closed in 1929. The enclosed water was drained completely in 1930, resulting in 20.000 hectare (one hectare is 100 square meter) land: the Wieringermeerpolder.
On May 23th, 1932, the enclosure dam was completely closed. And after locks and sluices, and a road on top of the dam were finished, it was officially opened in 1933. The now enclosed inner lake was slowly becoming a sweet water lake: fresh water enters from the river IJssel, and the water level is maintained by the sluices at the dam.
Originally, it was the plan to continue with the polder at the South-East, but priority was given to the somewhat smaller (and therefore easier to accomplish) drainage of the area in the North-East: the Noordoostpolder. Financial problems delayed the program, so the works on this polder only started in 1936. Two dikes, totaling a length of 55 kilometer were build: a dike from the Frisian village of Lemmer to the Isle of Urk, and a dike from the village of Vollenhove to the Isle of Urk. These dikes were finished during the first year of WW2 in the Netherlands, 1940. Two years later, the land was drained.
So, this is the situation at the end of the Second World War: the enclosure dam, with the monument at the site were the dam was closed, the Wieringermeerpolder in the North-West, and the Noordoostpolder in the North East. However, the Wieringermeerpolder had been flooded in the meantime: the retreating Germans had blown up the dike. Luckily, by then the water of the inner lake was already sweat. So, after the dike was repaired and the land had been drained again, it was directly suitable for farming.
In 1950, work begon on the most Southern project: the Flevopolder. Here, the experience acquired from the earlier drainage of the Noordoostpolder, made the engineers decide to alter Lely's original plans. Ground water from the neighboring 'old' land would flow to the new Noordoostpolder, resulting in subsidence and dehydration of the old land. To prevent this to happen with the new Flevopolders as well, it was decided to leave a strip of water between the new polder and the old land, even if this resulted in much more dikes to be constructed.
This project was so immens (almost 100.000 hectare) that it was divided in two separate drainage areas. The enclosing dikes of the Eastern part were finished in 1956, and the area was completely drained in 1957. The map below is from 1954 (or 1955), so the farmer ploughing his land is a bit early... This is a situation quite common in Dutch maps from this area: In an effort not to be outdated too soon, areas that were about to be drained were often drawn as if already completely drained and ready. Another anachronism can be seen at the Wieringermeerpolder: one of the emergency auxiliary pumps used to drain the area after the dike was destroyed in april 1945. These pumps were removed in december 1945.
As can be seen, the outline of the second, Western part of the Flevopolder has already been projected. Work on this would commence in 1959, the enclosing dikes were finished in 1957, and the land was completely drained in 1968.
Additionally, the outline of another, and final, polder can be seen: it runs from Enkhuizen to Lelystad, the new capital of the Polder Province, to the Isle of Marken and back to Enkhuizen again: The Markerwaardpolder. In the initial plans of Lely, this area was planned in continuity with the 'old' land, but in new plans, to prevent dehydration of the 'old' land, a strip of water between the polder and the 'old' land was foreseen, just like it had been done in the Flevopolders. A large canal between the Markerwaardpolder and the Flevopolders would keep Amsterdam and the IJsselmeer connected.
In 1963, construction of a dam between Enkhuizen and Lelystad was commenced. This dam was finished in 1975, and resulted in the division of the IJsselmeer. The new enclosed water was called the Markermeer (lake of Marken). But in the meantime, times had changed. Innovations in farming techniques had increased the yields per hectare, so the need for mor farming land was not as high as before. And was it wise to reduce the volume of a sweet water reservoir, when an increasing population resulted in an increasing water consumption. Additionally, the large area of sweet water became an important refuge for birds, and more and more people became aware of this unique environment. This resulted in strong protests against further reclamation plans.
Plans were continuously postponed and altered (in essence less land area, and larger water areas between old and new land), until in 2003 it was definitively decided by the Dutch government not to drain the Markermeer.
So, now it is not a polder, but a lake. Environmentally, it proved however quite a disappointing one: the lack of natural shores, as well as the fact that it is not connected to a river or the sea, resulted in a seabed completely covered with sediment. This resulted in a strong decline of life on the bottom of the lake, which on its turn resulted in a severe decline in fish and bird stock. The lake was dead.
But the Dutch were not the Dutch if they had not designed a solution: they used this sediment to create artificial islands in the lake. With natural shores, above the level of the lake (so no 'polders'), to attract birds. Additionally, it is foreseen that mussel banks return, that play a large role in filtering of the water.
So, how does this land area that never was, appear on a 2020 interactive map from the WHO? I don't know. But when you look at the shape of the area, the rim of water to the West and Southeast of it and the distance between the Southwest border and the city of Amsterdam, I am pretty sure it is not just a wrong software definition of land and water. Maps provided by ESRI, OpenStreetMaps or Google do not show the Markermeer as land. The WHO map does not state the primary source for the cartographic data.
Is this important? No. And it is always wise to follow WHO advise on global health and COVID-19. But just don't use their maps on your navigation system.